Don, is shipping to Mexico typically expensive? Perhaps a member north of the border can ship you perlite. I haven't worked with it, but it is pretty light weight stuff, correct? Hopefully that will minimize some of the shipping cost.

Nice oven work! Is it possible for you to post some pics of the hardboard mold you used for your oven? Also, how many parts water did you add to the 1:1.5 cement/perlite mix? Is the dome holding the temp quite well?

Sorry, i forgot making pics.I made it a viscous mass, so i don't know how much water it was actually. The dome became a 1mm crack during a 3.5h bake last week, but it's still in great shape. No need to worry